AQA A-LEVEL BIOLOGY: PAPER 1
2021 QUESTIONS AND CORRECT
ANSWERS
1.120Describe20the20induced20fit20model20of20enzyme20action20and20how20an20enzyme20acts20
as20a20catalyst.20-20ans--
20The20substrate20binds20to20the20active20site20and20forms20an20ES20complex.
-20The20active20site20changes20shape20slightly20so20it's20complimentary20to20the20substrate.
-20This20reduces20the20activation20energy.
1.220Tick20one20box20to20show20which20are20the20substrate20the20scientists20must20add20to20th
e20reaction20mixture20is20to20produce20ATP.20-20ans--20Adenosine20diphosphate.
1.320Suggest20and20explain20a20procedure20the20scientist20could20have20used20to20stop20each
20reaction.20-20ans--20The20nature20of20the20enzyme20by20putting20it20in20ice.
1.420Explain20the20change20in20ATP20concentration20with20increasing20inorganic20phosphate2
0concentration20-20ans--
20With20increasing20phosphate20concentration20more20ES20complex20is20form.
-20And20at204020mol20dm3,20all20active20sites20are20occupied.
2.120Explain20the20advantage20for20large20animals20of20having20a20specialised20system20that20
facilitates20oxygen20uptake.20-20ans--
20Large20organisms20have20a20smaller20surface20area20to20volume20ratio.
-20This20means20they20overcome20a20long20diffusion20pathway.
2.220Suggest20how20the20environmental20conditions20have20resulted20in20adaptations20of20sy
stems20using20model20A20rather20than20model20B.20-20ans--
20Water20is20more20dense20than20air.
-20So20it20supports20the20gills.
2.320A20student20studies20figure20320and20concluded20that20the20fish20gas20exchange20system
20is20more20efficient20than20the20human20gas20exchange20system.20Use20figure20320to20justify20
this20conclusion.20-20ans--
20The20difference20of20oxygen20concentration20between20the20artery20and20vein20is20larger20in2
0the20fish20than20the20human.
-20So20the20fish20remove20a20greater20amount20of20oxygen20that20they20intake.
, 2.420Explain20how20the20countercurrents20principle20allows20sufficient20oxygen20uptake20in20t
he20fish20gas20exchange20system.20-20ans--
20Blood20and20water20continuously20flow20in20opposite 20directions.
-20So20the20concentration20gradient20is20maintained20along20the20length20of20the20lamellae.
3.120Describe20how20one20amino20acid20is20added20to20a20polypeptide20that20is20being20forme
d20at20a20ribosome20during20translation.20-20ans--
20TRNA20brings20the20specific20amino20acid20to20the20ribosome.
-20The20anticodon20on20the20tRNA20binds20to20the20codon20on20the20mRNA.
-20The20amino20acids20join20to20form20a20peptide20bond20using20ATP.
3.220Use20information20in20table20to20to20suggest20why20this20amino20acid20replacement20cha
nges20the20properties20of20crystallin.20-20ans--
20The20hydrogen20bonds20form20instead20of20the20ionic20bonds.
-20And20it20changes20the20tertiary20structure20of20the20crystallin.
3.320MRNA20codon20for20the20non-mutant20triplets.20
mutated20mRNA20codon.20
Mutated20DNA20triplet.20-20ans--20AGG
-20GGG
-20CCC
4.120Suggest20two20ways20the20student20could20improve20the20quality20of20his20scientific20dra
wing20of20the20blood20vessels20in20this20dissection.20-20ans--20Add20labels.
-20Don't20use20shading.
4.220Describe20one20feature20that20allows20you20to20identify20the20blood20vessels.
Blood20vessel20X
Blood20vessel20Y
Feature20-20ans--20Artery
-20Vein
-20They20have20different20wall20thicknesses.
4.320Describe20two20precautions20the20student20should20take20when20clearing20away20after20t
he20dissection.20-20ans--20Disinfect20all20instruments.
-20Disinfect20hands.
5.120Describe20how20a20sample20of20chloroplasts20could20be20isolated20from20leaves.20-
20ans--20Break20open20the20cells20and20filter20it.
-20Keep20it20in20the20cold20to20ensure20it20has20the20same20water20potential.
-20Keep20it20in20a20controlled20pH.
-20Centrifuge20it20to20remove20cell20debris.
-20And20centrifuge20at20increase20in20speeds20so20the20chloroplast20can20settle20out.
2021 QUESTIONS AND CORRECT
ANSWERS
1.120Describe20the20induced20fit20model20of20enzyme20action20and20how20an20enzyme20acts20
as20a20catalyst.20-20ans--
20The20substrate20binds20to20the20active20site20and20forms20an20ES20complex.
-20The20active20site20changes20shape20slightly20so20it's20complimentary20to20the20substrate.
-20This20reduces20the20activation20energy.
1.220Tick20one20box20to20show20which20are20the20substrate20the20scientists20must20add20to20th
e20reaction20mixture20is20to20produce20ATP.20-20ans--20Adenosine20diphosphate.
1.320Suggest20and20explain20a20procedure20the20scientist20could20have20used20to20stop20each
20reaction.20-20ans--20The20nature20of20the20enzyme20by20putting20it20in20ice.
1.420Explain20the20change20in20ATP20concentration20with20increasing20inorganic20phosphate2
0concentration20-20ans--
20With20increasing20phosphate20concentration20more20ES20complex20is20form.
-20And20at204020mol20dm3,20all20active20sites20are20occupied.
2.120Explain20the20advantage20for20large20animals20of20having20a20specialised20system20that20
facilitates20oxygen20uptake.20-20ans--
20Large20organisms20have20a20smaller20surface20area20to20volume20ratio.
-20This20means20they20overcome20a20long20diffusion20pathway.
2.220Suggest20how20the20environmental20conditions20have20resulted20in20adaptations20of20sy
stems20using20model20A20rather20than20model20B.20-20ans--
20Water20is20more20dense20than20air.
-20So20it20supports20the20gills.
2.320A20student20studies20figure20320and20concluded20that20the20fish20gas20exchange20system
20is20more20efficient20than20the20human20gas20exchange20system.20Use20figure20320to20justify20
this20conclusion.20-20ans--
20The20difference20of20oxygen20concentration20between20the20artery20and20vein20is20larger20in2
0the20fish20than20the20human.
-20So20the20fish20remove20a20greater20amount20of20oxygen20that20they20intake.
, 2.420Explain20how20the20countercurrents20principle20allows20sufficient20oxygen20uptake20in20t
he20fish20gas20exchange20system.20-20ans--
20Blood20and20water20continuously20flow20in20opposite 20directions.
-20So20the20concentration20gradient20is20maintained20along20the20length20of20the20lamellae.
3.120Describe20how20one20amino20acid20is20added20to20a20polypeptide20that20is20being20forme
d20at20a20ribosome20during20translation.20-20ans--
20TRNA20brings20the20specific20amino20acid20to20the20ribosome.
-20The20anticodon20on20the20tRNA20binds20to20the20codon20on20the20mRNA.
-20The20amino20acids20join20to20form20a20peptide20bond20using20ATP.
3.220Use20information20in20table20to20to20suggest20why20this20amino20acid20replacement20cha
nges20the20properties20of20crystallin.20-20ans--
20The20hydrogen20bonds20form20instead20of20the20ionic20bonds.
-20And20it20changes20the20tertiary20structure20of20the20crystallin.
3.320MRNA20codon20for20the20non-mutant20triplets.20
mutated20mRNA20codon.20
Mutated20DNA20triplet.20-20ans--20AGG
-20GGG
-20CCC
4.120Suggest20two20ways20the20student20could20improve20the20quality20of20his20scientific20dra
wing20of20the20blood20vessels20in20this20dissection.20-20ans--20Add20labels.
-20Don't20use20shading.
4.220Describe20one20feature20that20allows20you20to20identify20the20blood20vessels.
Blood20vessel20X
Blood20vessel20Y
Feature20-20ans--20Artery
-20Vein
-20They20have20different20wall20thicknesses.
4.320Describe20two20precautions20the20student20should20take20when20clearing20away20after20t
he20dissection.20-20ans--20Disinfect20all20instruments.
-20Disinfect20hands.
5.120Describe20how20a20sample20of20chloroplasts20could20be20isolated20from20leaves.20-
20ans--20Break20open20the20cells20and20filter20it.
-20Keep20it20in20the20cold20to20ensure20it20has20the20same20water20potential.
-20Keep20it20in20a20controlled20pH.
-20Centrifuge20it20to20remove20cell20debris.
-20And20centrifuge20at20increase20in20speeds20so20the20chloroplast20can20settle20out.
